Generally, when a file is stored in a computer, a system of separately storing a meta data, and data or data files has been used. For example, in an environment using a plurality of computers connected by a network, some computers are used to store meta data and the remaining computers to store data files. In addition, even in the environment using a single computer, the storage location of the meta data and the data files may be separated.
In this environment, when the meta data are lost due to an accident, or the like, it is impossible to find where the stored position of the data files is, such that it is impossible to use the system even though a data area has been saved well.
In order to countermeasure the possibility of losing meta data, a method of periodically backing up an area in which meta data are stored may be considered, but cannot completely exclude the possibility of losing meta data due to the time intervals when the meta data are backed up, or the like.
Further, as in a system of providing a wastebasket function, a system of saving files to be deleted in a separate area such as a wastebasket, or the like, without immediately deleting the files to be deleted may be considered. In this case, a collision problem may occur at the time of recovering meta data after the meta data are lost. For example, a user deletes file ‘file1’ existing in a file storage path or a directory ‘A/B’, but the file ‘file1’ is not actually deleted from the data area by the wastebasket function. In this case, a new file ‘file1’ may be stored in the directory ‘/A/B’. Under this circumference, when the meta data are lost, which ‘file1’ to recover from the two ‘file1’ in the data area in the directory ‘/A/B’ becomes a serious problem.